Drawing process for production of round rods



Patented Mar. 27, 1934 UNITED STATES PATENT OFFICE Heinrich M61101, Ergste, near Schwerte, Germany No Drawing. Application October 3, 1928, Serial No. 310,189

1 Claim.

This invention relates to a drawing process for the production of brilliant polish round steel-rods of silver-steel, tool-steel, high speed-tool-steel or the like, free from pores and possessing absolutely uniform cross-section throughout.

Steel-rods of the kind mentioned are usually made from raw material which evidently neither does possess uniform cross-section, nor is it free from pores and brilliant polish.

Steel-rods, designed for example for making twist-drills for iron, must be made from steelrods of absolutely uniform cross-section, absolutely free from pores, of uniform hardness owing to the cutting edges, and brilliant polish.

These properties can be given to a work in a rational manner only by the drawing process. Owing to the great hardness and brittleness of the material, which generally possesses a high percentage of tungsten cobalt and the like, the article cannot be completed in one draw. It is necessary to draw several times and to heat and pickle again. The heating is generally carried out in an open reheating furnace or in a reheating vessel, as it is important to make the surface sufliciently soft for the draw, i. e. to produce as a rule a decarburization of the surface. Hereby the effect of the preceding draw is neutralized again, as the surface becomes again rough and of bad appearance. The result is, that very many draws have to be made until a perfect material is obtained.

A further inconvenience of this process consists in that, especially for thick material, the heating is not always uniform, wherefrom results that the surface of the rod is of unequal hardness. At the subsequent drawing and straightening of the rod the cross-sections of the rod become unequal. Owing to this unequal thickness of the rods it might happen that up to 50% and more rods have to go to the waste. The pickling of the material, necessary at each draw, might easily cause brittleness of the material through the pickling.

After termination of the drawing process the material is straightened, burnished and examined.

This commonly applied process is difficult, requires much time and great coinsumption of fuel, pickling liquid and the like, and it does besides not always supply articles fit for use.

The process, according to the invention does at the beginning not differ from the commonly used process. The material is first heated in coils, pickled and submitted to the first draw. It is then directly out into rods, bundled and heated in rods, which are much more suitable for a uniform heating than rings. After this heating the material is not brought into pickling liquid but into cleansing drums, containing each 500 to 600 kgs. of material which is ground with addition of grinding means, for instance emery, 12 to 24 hours. The heated and scales covered surface of the rods together with all pores and fissures is thereby removed.

The material is then polished in the usual manner and finally drawn by a loose draw of '65 0- to mm. reduction of diameter.

By the loose draw with the small reduction of diameter no fresh tensions are produced in the material.

The rods are perfectly uniform and they obtain a brilliant polish which could hitherto not be obtained.

In comparison with the grinding of the material on machines, which has also otherwise been employed and which allows to grind only one rod at the time, the grinding of rods in cleansing drums is much more advantageous, as a large quantity of rods is ground at a time, this requiring no attendance.

The fact, that the material is pickled only once, so does not only simplify the process but presents the further advantage that brittleness of the material caused by pickling is avoided.

The final slight draw to which the material is submitted, may be carried out, as it does not require any special skill, by an unskilled workman instead of by a skilled workman which was hitherto necessary, this unskilled workman being capable to attend several juxtaposed draw-plates.

When the improved process according to the invention is applied, no goods of unequal dimensions, i. e. no spoiled goods occur, with the exception of those goods which have direct defects of material.

I claim:-

A drawing process for producing highly polished round steel rods,,consisting in submitting the material in coil form to a first draw, in cutting the drawn material into straight rods, in subjecting these straight rods to strong heat, in tumbling and abrading the rods after the heating, and in then subjecting the rods to a light draw pass for smoothing the surface.

' HEINRICH MOLLER. 

